Water-submersible lighting devices are useful for a number of purposes and are especially useful for underwater lighting of swimming pools. Problems, however, include the difficulty and expense of installation, the difficulty of achieving watertight closure of the device so that short circuits or corrosion are avoided, the risk of electrical shock when substantial voltage is applied to the device, and the difficulty of replacing burned-out lamps. For example, some known underwater lights for swimming pools are permanently fixed below water level and are powered by residential power. Such lights require draining of water from the pool to replace a burned-out lamp. They also present the danger of high voltage electrical shock.